Method for packaging an integrated circuit device with stress buffer

Abstract

A method of fabricating a plurality of semiconductor devices includes attaching a plurality of integrated circuit (IC) die to a substrate including forming electric connections between contacts on the IC die and contacts on the substrate. After the IC die is attached to the substrate, a first encapsulating material is placed over stress-sensitive areas of the IC die. The first encapsulating material includes thirty percent or less of filler particles greater than a specified size. A second encapsulating material is placed over the first encapsulating material. The second encapsulating material includes sixty percent or more of filler particles.

What is claimed is: 
     
       1. A method for making a plurality of packaged integrated circuit devices comprising:
 placing a first layer of material with a modulus of elasticity greater than 0.1 and less than 3 GigaPascals (GPa) directly over a matrix of integrated circuit components and exposed portions of a first major surface of a substrate on which the integrated circuit components are mounted; 
 placing a second layer of material with a modulus of elasticity greater than 15 and less than 50 GPa over the first layer of material to encapsulate the integrated circuit components, the first layer and the second layer are conjoined before the first layer is placed over the matrix of integrated circuit components; and 
 singulating the substrate to form the plurality of packaged integrated circuit devices. 
 
     
     
       2. The method of  claim 1  further comprising:
 heating the first layer of material to a melting point temperature of the first layer of material; and 
 heating the second layer of material to a melting point temperature of the second layer of material until the second layer of material has melted. 
 
     
     
       3. The method of  claim 1  further comprising:
 molding the first layer of material and the second layer of material around the integrated circuit components and the exposed portions of the first major surface of the substrate. 
 
     
     
       4. The method of  claim 2  further comprising:
 heating the first and second layers of material to encapsulate the integrated circuit components and the exposed portions of the first major surface of the substrate. 
 
     
     
       5. The method of  claim 1  wherein:
 the first layer of material includes one of a group consisting of epoxy, acrylic, and silicone, with zero to thirty percent filler material. 
 
     
     
       6. The method of  claim 1  wherein:
 the second layer of material includes one of a group consisting of epoxy, acrylic and silicone, with sixty to ninety-five percent filler material. 
 
     
     
       7. The method of  claim 1  wherein:
 the substrate is one of a group consisting of a lead frame, a chip carrier, an organic substrate, and a ceramic substrate. 
 
     
     
       8. The method of  claim 1  wherein:
 a thickness of the first layer is between 20 and 100 microns and a thickness of the second layer is between 100 and 800 microns. 
 
     
     
       9. A method for making a packaged integrated circuit device comprising:
 attaching an integrated circuit component to a first major surface of a substrate; 
 positioning a sieve over stress-sensitive circuitry of the integrated circuit component, wherein the sieve is configured to form a cavity between the sieve and a top surface of the integrated circuit component; 
 attaching the sieve to the integrated circuit component, wherein the sieve includes a mesh attached to the integrated circuit component with an adhesive along edges of the mesh, and openings in the mesh are sized to allow a mold compound with particles less than a specified size to pass into the cavity; and 
 depositing the mold compound over the sieve, the integrated circuit component and exposed portions of the first major surface of the substrate, wherein the mold compound includes less than thirty percent of filler particles smaller than the specified size so that the cavity is filled with the mold compound without the filler particles larger than the specified size. 
 
     
     
       10. The method of  claim 9  wherein:
 the mold compound further includes one of a group consisting of epoxy, acrylic, and silicone. 
 
     
     
       11. The method of  claim 9  wherein:
 the substrate is one of a group consisting of a lead frame, a chip carrier, an organic substrate, and a ceramic substrate. 
 
     
     
       12. The method of  claim 9  wherein:
 a thickness of the cavity is between 20 and 100 microns and a thickness of the mold compound is between 100 and 800 microns. 
 
     
     
       13. The method of  claim 9  wherein the mesh is made of polymer, metal, or ceramic. 
     
     
       14. The method of  claim 9  further comprising applying the adhesive around at least two opposing edges of the mesh before attaching the sieve to the integrated circuit component. 
     
     
       15. A method of fabricating a plurality of semiconductor devices comprising:
 attaching a plurality of integrated circuit (IC) die to a substrate, wherein the attaching includes forming electric connections between contacts on the IC die and contacts on the substrate; 
 after the IC die is attached to the substrate, attaching a sieve over stress-sensitive areas of the IC die, wherein the sieve is configured to form a cavity between the sieve and a top surface of the IC die and includes openings sized to allow an encapsulating material with particles less than a specified size to pass into the cavity; and 
 depositing the encapsulating material over the sieve and exposed portions of the substrate, wherein the encapsulating material includes sixty to ninety-five percent of filler particles so that the cavity is filled with the encapsulating material without the filler particles larger than the specified size. 
 
     
     
       16. The method of  claim 15  wherein:
 the encapsulating material is a blanket layer of material that is melted or molded over the IC die and exposed portions of the substrate around the IC die. 
 
     
     
       17. The method of  claim 15  wherein:
 the encapsulating material further includes one of a group consisting of epoxy, acrylic, and silicone. 
 
     
     
       18. The method of  claim 15  wherein:
 the substrate is one of a group consisting of a lead frame, a chip carrier, an organic substrate, and a ceramic substrate. 
 
     
     
       19. The method of  claim 15  wherein:
 a thickness of the cavity is between 20 and 100 microns and a thickness of the encapsulating material is between 100 and 800 microns. 
 
     
     
       20. The method of  claim 15  wherein:
 the encapsulating material includes less than thirty percent of filler particles smaller than the specified size.